1. Field of the Invention
The present invention relates to an image processing apparatus with a memory, and a method for use therein.
2. Related Background Art
Owing to recent commercialization of the digital copying apparatus and development of the interface device for connecting such digital copying apparatus with an external equipment such as a host computer, there is becoming popular a system enabling image input from an image source other than the scanner provided in the digital copying apparatus.
However, such conventional configuration has been associated with the following drawbacks. The above-mentioned interface device is provided with a memory for storing image data transferred from the external equipment and is adapted to execute the printout of the image stored in said memory by the printer of the digital copying apparatus, according to a request from the external equipment, but the transfer of the image data from the external equipment cannot be executed until the completion of the print sequence, so that a significant time has been required in case of printing plural images. Also, in the case of transferring an image from the scanner of the digital copying apparatus to the external equipment, such image data transfer to the external equipment has been inhibited during the execution of the scanner sequence. Consequently, even if the digital copying apparatus is rendered capable of high-speed original scanning such as by an automatic document feeder, the scanned image data stored in the memory of the interface device cannot be transferred to the external equipment, and such point has been an obstacle in constructing the system.
Various digital color copying apparatus have recently been commercialized, and systems have been developed for printout of data such as of a computer graphic image from a host computer by connecting various interface device to such digital color copying apparatus.
In such conventional system, the image processing apparatus has been connected only to an image output apparatus for image formation on a recording medium, such as a digital color copying apparatus.
Such image processing apparatus, connected only to a single image output apparatus, is provided with a frame memory for storing the image data from the host computer. In such configuration, it has been proposed, if the capacity of such frame memory is sufficiently larger than the capacity of the image data to be printed, to divide said memory into two areas and to use one of said areas for image data entry from the host computer during the image data output from the other area to the digital color copying apparatus, thereby achieving image data input and output simultaneously and improving the efficiency of data processing.
Such data transfer method is called double buffer transfer and enables high-speed image data transfer.
However, in case of connecting two digital color copying apparatus of different printout processes, for example those of electrophotographic process and of ink jet process, there may result a difference in the method of utilization of the frame memory. More specifically, in the electrophotographic process, the data of an image are collectively stored, at one time, in the frame memory, whereas, in the ink jet process, the data of an image are stored and released in divided manner, in groups of controlled times, in the frame memory of a smaller size.
The color copying apparatus of electrophotographic process is usually designed with a maximum A3 print size, but that of ink jet process is often designed to print up to A1 size at maximum. The image processing apparatus equipped with such two color copying apparatus will require a frame memory corresponding to the A3 size, but a frame memory corresponding to A1 size is not favorable in consideration of the cost. As shown in FIGS. 1A and 1B, R, G, B full-color signals for the A3 size require a memory capacity of 96 MB. On the other hand, those for the A1 size require a capacity of four times that, or 384 MB. On the other hand, the ink jet recording process can achieve printing of an A1-sized image, by storing image data into the frame memory only for the hatched portion shown in FIG. 36 at each time and by repeating such data storage.
Now, let us consider a case where the image processing apparatus has a frame memory capacity corresponding to A3 size and is provided with a digital color copying apparatus of electrophotographic process and another digital color copying apparatus of ink jet process. In such configuration, if it is desired to print the A4-sized image data only from the digital color copying apparatus of electrophotographic process, high-speed image data transfer is possible by dividing the frame memory into two areas and effecting the double buffer transfer as explained in the foregoing. However if it is desired to effect printing also in the copying apparatus of the ink jet process, proper image output cannot be obtained since the frame memory is fully occupied for the double buffer transfer in the first and second memory areas.
Besides, while the printout of the electrophotographic process can be completed within an extremely short time, that of the ink jet process requires a very long time, thus occupying the frame memory for a long time.